Protecting compromised tissues, as in the case of lacerated skin or mucous membrane, has been of interest to clinicians for decades. This commenced by using the now-described “traditional bandage.” This was followed by the development of adhering, highly conformable, thin film, such as Opsite Flexigrid® (marketed by Smith & Nephew) and similar systems later on. The Opsite Flexigrid® consists of a thin polyurethane membrane coated with a layer of an acrylic adhesive. The dressing, which is permeable to both water vapor and oxygen, is impermeable to micro-organisms. Once in position, the film provides an effective barrier to external contamination, while producing a moist environment at the surface of the wound by reducing water vapor loss from the exposed tissue. Under these conditions in shallow wounds, scab formation is prevented and epidermal regeneration takes place at an enhanced rate, compared with that which occurs in wounds treated with traditional dry dressings. The polyurethane film is supported on a removable flexible carrier that can be drawn upon to provide a record of the size and shape of the wound to which the dressing is applied. Opsite Flexigrid® was recommended by the manufacturer for use in the treatment of scalds, first- or second-degree burns, donor sites, post-operative wounds, minor injuries (including abrasions and lacerations), and for the prevention and treatment of superficial pressure areas. Larger sizes of the dressing without the flexible carrier are marketed as incise drapes. Concomitant with the development of Opsite and similar films, a few investigators pursued the development of the so-called liquid bandages as discussed in the following paragraphs.
Naturally occurring and derivatized naturally occurring polymers have been tested as liquid adhesive coatings for bandage applications and, in some cases, utilized commercially. Typical examples are nitrocellulose in various solvents (e.g., New Skin-Medtech Laboratories, Inc., Cody, Wyo.), agar in water and diethylene glycol (U.S. Pat. No. 4,291,025), carrageenan and hydroxypropylmethyl cellulose in water (U.S. Pat. No. 4,318,746), and alginate in glycerin (U.S. Pat. No. 4,393,048). All of these natural polymers can support microbial growth, hence requiring the addition of a preservative or antimicrobial agent to the product. The liquid bandages based on water, diethylene glycol, glycerin, etc., are not only susceptible to microbial growth, but are often also slow drying due to high heats of vaporization; and are often water sensitive, which can result in problems when used on areas of the body exposed to water. One commercial product, New Skin, does dry rapidly and is not water sensitive, but can cause stinging and further irritation of the skin upon application.
A few synthetic polymers have been patented for use as liquid adhesive coatings for bandage applications, most notably polymers containing 2-hydroxyethyl methacrylate (U.S. Pat. No. 4,303,066). These bandages based on the use of solvents can sting abraded areas; and the films can swell and wash off when in contact with water. U.S. Pat. No. 4,569,784 claims an ointment, not a long-lasting bandage composed of an emulsion of water and silicone fluids, among other fluids. This reference can provide for an immediate soothing, but often not long-lasting, treatment of the skin or mucous membranes. It also does not provide for fast drying, abrasion resistance, and other attributes which a polymer film can provide.
Additionally, traditional wound and surgical bandages, such as Band-Aids (Johnson & Johnson, New Brunswick, N.J.), comprised of film backings with adhesive, may contain silicones as part of either the adhesive or the backing (e.g., U.S. Pat. No. 4,650,817). These products are not applied as liquid adhesive coating where films form and adhere directly on the skin. This led Salamone et al., (U.S. Pat. No. 4,987,893) to develop a liquid polymer-containing coating material which can act as a bandage or dressing to protect wounds, when applied in liquid form and air-dried on the wound to form an adherent, solid protective film without significant stinging to the skin or mucous membranes of the user. The liquid polymer-containing coating material of U.S. Pat. No. 4,987,893 was noted to consist essentially of a siloxane-containing polymer and a solvent system comprising a polar solvent in small amount and a volatile liquid which is non-stinging to a user but provides bulk and formability to the liquid. Preferably, the polymer is present from 1 to 40% by weight, the volatile liquid from 59.9 to 98.9% by weight and the polar solvent from 0.1 to 10% by weight. When the polar solvent is eliminated, the volatile liquid can be in amounts of 60 to 99%. The solvent is minimized to obtain flowability desired at the lowest solvent level feasible which minimizes stinging. The material forms a coating or bandage in the form of a dried film when applied to a surface or the skin of a user.
Collectively, U.S. Pat. No. 4,987,893 claims that combinations of alky siloxy siloxane-containing polymers admixed with liquid polydimethylsiloxanes are excellent non-stinging, non-irritating liquid coating material for forming films which act as conformable bandages adhering to and protecting nails, skin, and mucous membrane wounds from abrasion, contamination, and desiccation, while stopping pain from exposed nerve ends and allowing body fluid evaporation.
However to those skilled in the art of polymers, the compositions of U.S. Pat. No. 4,987,893 are (1) expected to result in low tear strength films because of being made of polysiloxane-based chains; (2) not expected to form, in a timely manner, a solid film at the application site because of the low volatility of their major constituents; (3) expected to yield hydrophobic films that have low or no tendency to adhere to moist tissue for sufficient periods of time—these films offer no advantage over regular bandages; and (4) not expected to yield thin film on difficult-to-reach areas. Such undesirable features of U.S. Pat. No. 4,987,893, and the prior art that preceded this patent provided a strong incentive to explore the development of the amphiphilic, water-insoluble spray-on liquid compositions subject of this invention which have been noted to represent a series of preferred medicated and unmedicated alternatives to regular bandages and all so-called liquid bandages of the prior art. A special incentive to explore the development of certain segments of the present invention dealing with pain-free, film-forming compositions was related to the effective use of Nobecutane spray as a temporary dressing of skin graft donor sites [Brodovsky, S., et al., J. Dermatol. Surg. Oncol., 12(4), 386 (1986)] in spite of using the stingy ethyl acetate as solvent. The respective clinicians noted that various methods have been used for managing split-thickness skin graft donor sites. Open and closed techniques have been suggested by various authors with the purpose of achieving smooth and rapid healing of the wound. There is growing evidence to suggest that the site and quality of the healing is improved when the wound is protected from dehydration and further mechanical trauma. A recent method is the spraying of Nobecutane Spray on the donor site. Nobecutane sprayed on a wound forms a plastic film which serves as a dressing material. It contains specially modified acrylic resin in an organic solvent (ethyl acetate) and TMTD (tetramethylthiuram disulphide) which is strongly bactericidal and fungicidal. This method was used on 50 patients and found to be effective in achieving rapid and painless healing. The dressing is transparent, permits easy follow-up of healing in the donor site, protects the wound against infection, and does not inconvenience the patient. The treatment is simple, economical, and does not require special skills. The dressing peels off spontaneously after epidermal regeneration of the wound is completed. No complications or allergic reaction were observed with this treatment.
A commercial spray bandage sold under the trade name Curad® Spray Bandage (Beiersdorf, Inc., Winton, Conn.) was described to have the following ingredients: poly(methyl acrylate-isobutene-mono-isopropyl maleate), ethyl acetate, menthol, pentane, and carbon dioxide. It was noted to yield a transparent, breatheable film that seals applications site from water, dirt, and germs for maximum protection. A second bandage spray that is water-soluble is commercialized by Swift First Aid as Swift Bandage Spray. It is advertised to provide an invisible coat for protection from dire, dust, and bacteria. It has been recommended for minor injuries, irritations, and insect bites. The inactive ingredients of the spray-on are ethyl alcohol, isobutane, n-butane, propane, a water-soluble copolymer of N-vinyl pyrrolidone, and vinyl acetate. The spray-on also contains benzethonium chloride (0.2% w/w) and benzocaine (5% w/w) as active ingredients. Unfortunately, this coating is not expected to reside for a practically effective period of time at the application site because of its water solubility.
None of the cited prior art has described or made obvious the conception of the spray-on compositions of the amphiphilic, non-water-soluble, segmented/block copolymers that are capable of yielding conformable, high compliance film with modulated oxygen permeability and water vapor transmission which are the subject of the present invention.